Goodwill By Reportable Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill	$ 259,357	$ 254,685
Accumulated impairment of goodwill	(151,229)	(151,229)
Total	108,128	103,456
Photonics
Goodwill [Line Items]
Goodwill	136,278	136,321
Accumulated impairment of goodwill	(102,461)	(102,461)
Total	33,817	33,860
Vision
Goodwill [Line Items]
Goodwill	89,116	84,401
Accumulated impairment of goodwill	(31,722)	(31,722)
Total	57,394	52,679
Precision Motion
Goodwill [Line Items]
Goodwill	33,963	33,963
Accumulated impairment of goodwill	(17,046)	(17,046)
Total	$ 16,917	$ 16,917